China Mechanical Engineering

Design of a Kind of Multi-dimensional Attitude Adjustment and Vibration Isolation Platform Based on 4-UPS/CPC Parallel Mechanisms#br#

ZHANG Ying, SUN Hao, MA Shuaishuai

2021, 32(13): 1513-1522,1529. DOI: 10.3969/j.issn.1004-132X.2021.13.001

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A kind of multi-dimensional attitude adjustment and vibration isolation platform （MDAA&VIP） was presented for the wheel legged robot carriers. With 4-UPS/CPC parallel mechanisms as the main body and spring damping module as supplementary， the functions of attitude adjustment and vibration isolation were combined in the proposed MDAA&VIP to meet the needs of attitude adjustment and vibration isolation during the working processes of the carriers. Taking the combination of working space， static stiffness and dexterity as the objectives， and the structural parameters of the 4-UPS/CPC parallel mechanisms were optimized. The road spectrum model was established and the length of each limb needed to keep the upper platform horizontal was predicted by using the differential prediction algorithm when the carriers walked on the C-level roads. The effectiveness of the attitude adjustment function of the designed platform was verified by simulations. The vibration model of multi-dimensional vibration isolation system was established， and the vibration response of the system was studied by theoretical and simulation methods under forced vibrations. The results show that the isolation rates of the platform in five degrees of freedom directions are above 57%. The prototype of vibration isolation platform was designed and the experimental system was set up， and the vibration isolation experiments in X， Y and Z directions were carried out. The experimental results show that the designed MDAA&VIP has good vibration isolation performance， and the vibration isolation rates in the three test directions are more than 50%.

RUL Prediction of High-power Semiconductor Lasers Based on Cluster Sampling and SVR Model#br#

YAN Jianwen, ZHONG Xiaohu, FAN Yu, GUO Sanmin,

2021, 32(13): 1523-1529. DOI: 10.3969/j.issn.1004-132X.2021.13.002

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RUL prediction was the core problem of reliability evaluation of high-power semiconductor lasers under various environmental stresses. In practical applications， the existing SVR methods all focused on minimizing the overall errors of the regression curve of the trained model， so as to pursue the generalization， which often resulted in unsatisfactory prediction results at the critical early warning stage， especially before the near-failure， and failed to ensure its reliability. Therefore， the SVR model training method was proposed based on cluster sampling. The observation data in the later period of the test samples were sampled for multiple cluster and then used for the SVR model test. The parameters in the SVR model made the SVR model fit the data in the later period of the training samples better. The effectiveness and robustness of the proposed method were verified by a case study， the results show that the performance and practical value of the proposed method are better than those of several representative small sample analysis methods.

Generation Method of Dimension Correlation Change Propagation Paths

YANG Bo, SHANG Junzhi, MA NingGAO Changqing

2021, 32(13): 1530-1538. DOI: 10.3969/j.issn.1004-132X.2021.13.003

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From the view point of dimension change propagation among parts and parts related dimensions， a searching method of dimension change propagation paths was discussed based on correlation. The dimension correlation model for change propagation was established to describe the hierarchical and logical relationship between dimension characteristics. By using matrix operation method， the correlation change propagation network with parts as nodes was established based on dimension correlation. The dimension change propagation coefficient was used as the evaluation index to optimize the paths. The set value matrix， intermediate transformation matrix and vector value matrix were established for representing the correlation between the dimension parameters of the changed parts and the affected parts. By using the inner product operation， the correlation mapping relationship between the changed dimensions and the dimension parameters of the affected parts was established， and the propagating processes and paths of changed dimension in products were determined. Finally， an example for size change in propagation processes of paper printing and laminating machine was given to verify the effectiveness of the proposed method.

Industrial Robot Calibration Based on Improved IGG3 Weight Function of Distance Error Model#br#

ZHANG Enzheng, TANG Ningmin, CHEN Gang, LIU Cuiping

2021, 32(13): 1539-1546. DOI: 10.3969/j.issn.1004-132X.2021.13.004

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In calibration processes of industrial robots， measurement gross error data might have effects on the accuracy of calibration results， therefore， an industrial robot calibration method was proposed based on improved IGG3 weight function of distance error model， which was to further improve calibration accuracy of industrial robots by using improved IGG3 weight function least square identification algorithm. The SR4C industrial robot was taken as the research object， the mathematical model of robot distance error was established， the least square identification algorithm of IGG3 weight function was studied theoretically. A robot calibration experimental system was constructed and calibration experiments were performed based on improved IGG3 weight function of distance error model， the experimental results show that the proposed method may effectively reduce the effects of gross error data on the calibration accuracy. The proposed method may be used in the field of industrial robot calibration to improve the positioning accuracy of industrial robots.

Analysis of Magneto-optical Imaging Characteristics of Weld Defects under Alternating Magnetic Fields#br#

LI Yanfeng, JI Yukun, GAO Xiangdong, ZHANG Yanxi, SUN Yousong, XIAO Xiaoting, PAN Chunrong

2021, 32(13): 1547-1554. DOI: 10.3969/j.issn.1004-132X.2021.13.005

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A method of detecting the weld defects was studied based on MO imaging. According to the Faraday rotation effect， the key to detect weld defects under alternating magnetic fields was to accurately describe the relationship between the magneto-optical imaging characteristics of weld defects and the leakage magnetic field. A three-dimensional finite element model of weld defects was established， and the leakage magnetic field distribution of different types and widths of defects was simulated. MO imaging nondestructive testing （NDT） tests were carried out to detect different weld defects under an alternating magnetic field excitation. The validity of a finite element model was verified by the tests. The results show that the leakage magnetic field distribution is closely related to the types and widths of the defects. With the widths increase， the vertical components of magnetic induction intensity of defect leakage magnetic field increase. Under the same width conditions， the peak-to-valley gray values of incomplete fusion， surface crack， subsurface crack and no defect show a decreasing trend. The gray values of a MO image may match the corresponding magnetic field intensities. The proposed weld defect model and MO imaging tests may effectively describe the influences of different weld defects on the distribution of magnetic flux leakage signals and image gray values， which are helpful to improve the weld defect detection and quality assessment.

Multi-objective Optimization of Cutting Parameters in Ti6Al4V Milling Processes Based on Finite Element Simulation#br#

LI Yujia, HUANG Bing, LU Juan, ZHONG Qijing, CHEN Chaoyi, LIAO Xiaoping, MA Junyan

2021, 32(13): 1555-1561,1570. DOI: 10.3969/j.issn.1004-132X.2021.13.006

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In order to make the cutting processes meet the requirements of environmentally conscious manufacturing（ECM）， for the quality index（surface roughness） and ECM index（energy consumption）， aiming at the Ti6Al4V processes， the Gaussian process regression（GPR） method optimized by artificial bee colony （ABC） algorithm was used to established the finite element agent model， and the processing parameters satisfying the optimal machining objectives were obtained by using the multi-objective particle swarm optimization（MOPSO） algorithm. Deform-3D， a finite element simulation software which might reduce the testing cost was used to obtain the surface roughness and energy consumption data corresponding to each milling parameter combinations， and the effectiveness was proved by physical tests. Then， an improved GPR method was used to establish the prediction model based on the surface roughness and energy consumption of the finite element simulation data. The performance of the model was compared with that of the other two models， and the advantages of the improved model in accuracy and response time were proved. Finally， Pareto front of processing parameters with the goal of minimum energy consumption and excellent surface quality were obtained by MOPSO algorithm. The effectiveness of the ABC-GPR-MOPSO algorithm was verified by physical tests.

Flow Field Design and Process Stability in Electrochemical Machining of Involute Internal Splines#br#

WANG Yiyu, ZHAO Jianshe, GU Minkai, JI Tao

2021, 32(13): 1562-1570. DOI: 10.3969/j.issn.1004-132X.2021.13.007

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In order to further improve the process stability in electrochemical machining of involute internal splines， the influence rules of electrolyte flow pattern， tool cathode structure and electrolyte parameters on the flow field distribution were discussed based on numerical analysis. The numerical analysis results show that the side flow of electrolyte may enhance the uniformity of electrolyte velocity distribution at the inlets of the machining regions， and the variable cathode with guide may reduce the velocity fluctuation of workpiece surfaces. In view of the process stability and localization， the electrochemical machining tests of the involute internal splines were carried out. The testing results show that the feed rate may reach more than 2.1 mm/min， the tooth profile deviation may be controlled within 0.015 mm， the helical deviation may be controlled within 0.02 mm when the processing depth is as 30 mm. The efficiency and precision of machining method may meet many practical requirements and has obvious technical and economic advantages.

Research on Fracture Simulation of Wheel Hubs for Small Overlap Crashs

ZHENG Hao, OUYANG Jun, WANG Yuchao, LI Wei, ZENG Zicong, HUANG Yi, LIU Heng

2021, 32(13): 1571-1576,1583. DOI: 10.3969/j.issn.1004-132X.2021.13.008

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In order to predict the crash fracture behavior of wheel hubs precisely， the material fracture mechanics tests for AlSi7（casting aluminum） were carried out and material characterization parameter fitting method was studied based on CrachFEM failure criterion. Modeling rules of finite element and methods of material failure parameter modification suitable for wheel hub fracture simulation were proposed，the simulation results of crash fracture mode for wheel hubs are more consistent with the test results according to the comparative analysis of quasi-static and dynamic tests and simulations for wheel hubs. The results show that the accuracy of crash fracture simulation is improved after using the proposed modeling rules and methods， which may provide effective method of virtual simulation evaluation for small overlap crashs.

Vision Measurement Method for Ground Surface Roughness Based on Color Image Singular Value Entropy Index#br#

YI Huaian, ZHAO Xinjia, TANG Le, CHEN Yonglun

2021, 32(13): 1577-1583. DOI: 10.3969/j.issn.1004-132X.2021.13.009

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Most of the evaluation indices used in measuring surface roughness by machine vision were statistical analyzed based on gray scale image information， while some evaluation indices based on color information did not provide reasonable mathematical structure expression in current studies.Aiming at these problems， a detection method was proposed based on singular value entropy of color images to evaluate the roughness of ground surfaces.According to the differences of the energy distribution of the virtual image formed by the color-block on the surfaces with different levels of roughness， a pure quaternion data structure was used to characterize a color image and the data was analyzed. The singular value entropy was extracted as the evaluation index， and the feasibility of evaluating ground surface roughness was demonstrated based on singular value entropy index.The experimental results show that the singular value entropy of color images is a reasonable and feasible surface roughness evaluation index， and has a reasonable data structure expression in a mathematical sense. The comparative analysis of relevant index proves that the correlation and applicability of the index with surface roughness are stronger than that of the color difference index， and the regression prediction results are relatively accurate and have the potential to be extended to the field of engineering applications.

Lightweight Optimization Design of Side Collision Safety Parts for BIW Based on Pareto Mining#br#

WANG Dengfeng, LI Shenhua

2021, 32(13): 1584-1590,1637. DOI: 10.3969/j.issn.1004-132X.2021.13.010

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To improve the lightweight optimization effectiveness of BIWs， the entropy weight gray correlation analysis method was proposed to mine the optimal solutions in the non-dominated Pareto solution sets. The side impact finite element models of BIW and full vehicle were established， and the validity of the built model was verified by the side collision tests of vehicles. Taking the thicknesses of side impact safety parts as the design variables， considering the basic static-dynamic performance and side impact safety performance of BIW， the radial basis function neural network and Kriging（RBFNN-Kriging） hybrid approximate model combined with non-dominated sorting genetic algorithm Ⅱ（NSGA-Ⅱ） was constructed for multi-objective optimization. Finally， entropy weight gray correlation analysis method was proposed for calculating the gray correlation grade of all non-dominated Pareto solutions， and the gray correlation grade was taken as evaluation index to use for multi-objective decision. The optimization decision results show that the mass of side impact safety parts for BIW is reduced by 2.68 kg under the requirements of BIW performance design baseline，the good lightweight effectiveness is achieved.

Effects of Water-based Hybrid Nanofluids on Internal Cooling Grinding Performance#br#

PENG Ruitao, PENG Xing, TONG Jiawei, ZHAO Linfeng, CHEN Meiliang, HE Xiangbo

2021, 32(13): 1591-1599. DOI: 10.3969/j.issn.1004-132X.2021.13.011

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Multi-walled carbon nanotubes（MWCNTs)， molybdenum disulfide（MoS2)， ionic liquid （1-ethyl-3-methylimidazolium tetrafluoroborate，［EMIm］BF4) and gum arabic（GA) were used to prepare stable dispersed water-based ILs-MWCNTs/MoS2 hybrid nanofluids.The tribological and thermophysical properties of hybrid nanofluids were studied，and the internal cooling grinding tests of hybrid nanofluids were compared with those of traditional grinding fluids， the grinding temperature and surface integrity of the two kinds of grinding fluids were analyzed.The results show that the grinding temperature， surface roughness and microhardness of hybrid nanofluids are reduced by 8.1%， 21.4% and 6.56%， respectively， the residual compressive stress is increased by 11.6 MPa， and the surface morphology is smoother and more regular. Therefore， the hybrid nanofluids reflect better grinding performance.The energy dispersive spectrometer（EDS) analysis results show that under the physical synergistic strengthening of ionic liquids and nanoparticles， the hybrid nanofluids exhibit excellent cooling and lubricating properties， and improve the grinding performance.

Mechanics Model and Uniform Material Removal Tests of Functionally Graded Lapping and Polishing Plates#br#

DONG Xiaoxing, LU Congda, JIN Mingsheng, WEN Donghui, JI Shiming, WANG Liming, ZHU Dongjie,

2021, 32(13): 1600-1607. DOI: 10.3969/j.issn.1004-132X.2021.13.012

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Aiming at the problems of non-uniform material removal， a novel processing method was proposed based on functionally graded lapping and polishing plate（FG-LPP）. Taking the Preston equation as the theoretical basis， the numerical simulation and elastic mechanics calculation of the contact stress between the FG-LPP and the workpiece were carried out. The semi-inverse solution method was used to deduce the contact stress equation， a set of the prediction system about two-layer structure mechanics model of the FG-LPP and the workpiece material removal level were established. The material removal rate（MRR） lapping tests of different parts were carried out on ZrO2 ceramics， and the standard deviation of the average MRR was used as the evaluation standard of the uniformity removal in each area. The testing results show that in three time periods of 0~30 min，30~60 min，60~90 min， the standard deviations of the processed FG-LPP are as 6.47 nm/min， 3.76 nm/min， and 5.09 nm/min， while the corresponding values of the common lapping and polishing plate are as 55.23 nm/min， 54.73 nm/min and 35.92 nm/min， respectively. Two types of plates are maintained at a removal rate of 150~400 nm/min， but the FG-LPP may simultaneously achieve uniform removal of materials during the machining processes， reduce the finishing process steps of the workpiece after lapping， and make the machining processes simple and efficient.

Experimental Research of CFRP Cutting by Using Water Jet Guided Laser Processing#br#

WANG Jianxin, WU Yaowen, ZHANG Guangyi, CHAO Yang, ZHANG Wenwu,

2021, 32(13): 1608-1616. DOI: 10.3969/j.issn.1004-132X.2021.13.013

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The key processing parameters of water jet guided laser cutting CFRP were studied by orthogonal test method， the effects of feed rate， water jet velocity， pulse frequency and laser power on cutting CFRP were obtained， and the optimal parameters obtained by direct comparison method and range analysis method were compared for single grooving cutting. The results show that when cutting CFRP under the optimal parameters obtained by range analysis method， the kerf depth increases by 3.2%， the kerf width decreases by 9.2%， the kerf taper decreases by 11.8%， and the line roughness decreases by 40.2%. Compared with the dry laser processing method， it is found that the water jet guided laser processing technology has obvious advantages in cutting CFRP. Due to the scouring and cooling effects of water jet， there is almost no heat affected zone and fiber pull-out on the cutting surfaces of the materials. In addition， the optimal processing parameters were obtained by orthogonal test， and the taper-free cutting of 4 mm thick CFRP was realized by using these parameters.

An Multi-objective Optimized Production Scheduling for Automobile Prototype Workshops Considering Employee Work Ability#br#

YI Qian, HE Shuang, NING Qing, LI Congbo, YI Shuping

2021, 32(13): 1617-1629. DOI: 10.3969/j.issn.1004-132X.2021.13.014

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The reasonable scheduling scheme of employee-task in the automobile prototype workshop was the key to ensure the smooth progress of production. In view of the characteristics and existing problems of automobile prototype workshops， an evaluation system of employee work ability was designed based on decision-making trial and evaluation laboratory-analytic network process（DEMATEL-ANP） method. On account of the quantitative assessment of employee work ability， a workshop scheduling optimization model was established considering employee work ability， aiming at the makespan， the balance degree of skill utilization and labor cost. A non-dominated sorting genetic algorithm-Ⅱ（NSGA-Ⅱ） based on technique for order preference by similarity to ideal solution（TOPSIS） was adopted to solve the model and get the relative optimal solution. Finally， the feasibility and effectiveness of the proposed model and method were verified through practical production cases.

Structural Design and Performance Analysis of New Micro Convex Fins in Plate-fin Heat Exchangers#br#

PENG Xiang, LI Denghong, LI Jiquan, JIANG Shaofei

2021, 32(13): 1630-1637. DOI: 10.3969/j.issn.1004-132X.2021.13.015

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In order to improve heat transfer efficiency in fin regions and the overall heat transfer performance of plate-fin heat exchangers， a new micro convex fin structure was proposed. An approximate model was constructed based on the simulation results of thermodynamic performance at multiple sampling points of the structure parameters. With the total heat transfer rate as optimization objective and the pressure drop as the constraint， the optimum structure parameters （micro convex height， micro convex angle， micro convex opening length） of micro convex were determined by using sequential quadratic programming algorithm. And the arrangement spaces and arrangement type of micro convex were optimized to determine the specific parameters of improved micro convex fin structures. Through the temperature and pressure field analysis of fin channels， and the comparison of heat transfer performance with the same size of straight fin， the effectiveness of the new micro convex fin structure was verified.

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